Did you set the flow rate of the control zone terminal unit to 0? If so, this is causing the warning. Set it to some other small value, but not too small since the control zone fraction is used to determine the total load on the unitary system coils.
Total Load (W) = control zone load (W) / control zone fraction.
You should also notice by this equation that if the control zone load is always 0 (thermostat never calculates a cooling or heating load), then the coils should not turn on. So yes that is one way to get only ventilation air if the fan is set to "constant fan mode". If the fan is set to "cycling fan mode" then the fan will never turn on.
Another way would be to use the coil availability schedules to schedule the coils off all year.
On 6/4/2011 12:35 AM, Vinay Devanathan wrote:
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